This is an application for a Mentored Research Scientist Career Development Award. The candidate proposes an organized program of training and research with the overarching goal of integrating 1) theoretical and technical knowledge of early brain and behavioral development; 2) expertise in functional magnetic resonance imaging (fMRI); 3) knowledge of core deficits in autism as well as the underlying brain mechanisms in this disorder; 4) technical expertise in the behavioral methods required for successful fMRI scanning of young children; 5) proficiency in statistical methods for longitudinal studies; and 6) knowledge of the biological basis of social cognition, in a program of research aimed at elucidating the development and neural basis of social cognition deficits in children with autism. The candidate's training as a developmental psychologist and cognitive neuroscientist has allowed him to develop expertise in the first two of the six areas listed above. Now, to establish a career as a productive and independent autism investigator, the applicant will obtain additional training in the remaining four disciplines. The neurobiological basis and developmental course of social cognition deficits in children with autism remain poorly understood. Likewise, little is known about the neural correlates of social cognition in typically developing children or about the changes in brain function that support normative social cognitive development. Building upon the training outlined in this award proposal, the candidate will initiate a series of fMRI studies to characterize the neural circuitry underlying aspects of social cognition in typically developing children and children with autism (ages 4-10 years). These studies will thus extend the candidate's prior and ongoing work in fMRI and social cognition and provide an initial step in a program of research with the long term goal of systematically exploding the development and neural basis of social cognition through longitudinal fMRI studies of social cognition in healthy children and children with autism.